Flash memory devices have developed into a popular source of non-volatile memory for a wide range of electronic applications. Flash memory devices typically use a one-transistor memory cell that allows for high memory densities, high reliability, and low power consumption. Changes in threshold voltage of the cells, through programming of charge storage structures (e.g., floating gates or charge traps) or other physical phenomena, determine the data value of each cell. Common uses for flash memory and other non-volatile memory include personal computers, personal digital assistants (PDAs), digital cameras, digital media players, digital recorders, games, appliances, vehicles, wireless devices, mobile telephones, and removable memory modules, and the uses for non-volatile memory continue to expand.
A Flash memory can be erased and reprogrammed in blocks instead of one byte at a time. A typical Flash memory comprises a memory array, which includes a large number of memory cells. Each of the memory cells includes a floating gate field-effect transistor capable of holding a charge. The data in a cell is determined by the presence or absence of the charge in the charge storage structure. The cells are usually grouped into sections called “erase blocks.” The memory cells of a Flash memory array are typically arranged into a “NOR” architecture (the cells arranged in an array of rows and columns, each cell directly coupled to a bit line) or a “NAND” architecture (cells coupled into “strings” of cells, such that each cell is coupled indirectly to a bit line and requires activating the other cells of the string for access). Each of the cells within an erase block can be electrically programmed charging the floating gate (or other charge storage structure.) The charge can be removed from the floating gate by a block erase operation, wherein all memory cells in the erase block are erased in a single operation. Other types of non-volatile memory include, but are not limited to, Polymer Memory, Ferroelectric Random Access Memory (FeRAM), Ovionics Unified Memory (OUM), Nitride Read Only Memory (NROM), Carbon Nanotube memory, Magnetoresistive Random Access Memory (MRAM) and phase change memory (PCM).
NOR architecture memories may have problems if a single cell in a column becomes unprogrammable (e.g., a cell that has been determined to have failed, and/or has otherwise become bad, unreliable, faulty, etc.) Specifically, a single unprogrammable cell in a column in a NOR memory can be leaky and affect the entire column. Repair of an entire column during a program operation can take longer than the low program latency of the operation allows, leading to problems with speed of operation.
For the reasons stated above, and for other reasons which will become apparent to those skilled in the art upon reading and understanding the present specification, there is a need in the art for performing column repair in memories.